Conventional automatic volume control systems for radio receivers use a signal voltage developed in the detector to control the amplification or gain of the radio frequency and/or intermediate frequency stages of the radio. Thus some variation in gain control signal is required. Also, with amplitude modulated radio systems, the audio frequency output is proportional to the radio or intermediate frequency signal at the detector. It follows that for a given modulation the audio frequency output is proportional to the automatic gain control signal from the detector stage and thus varies with the strength of the radio frequency signal received at the detector. Thus the conventional automatic gain control system can reduce but cannot eliminate changes in audio output with changes in the received signal strength.
It is, accordingly, an object of the invention to vary the amplification of the audio amplifier of a radio generally inversely as the strength of the automatic gain control signal.